If I remember correctly, all the lizards were once some kind of dragons created by Zorl-Stissa but then had to be turned into lizards because of the impending extinction caused by a conflict between them and the other 6 races which was later undone by the Red Prince and the Red Princess.
It could be that Zorl-Stissa created these dragons in the likeness of the omnipotent, universe creating dragons like the Patriarch, but less powerful.
There was also put much emphasis on these lesser dragons being red, like the Prince and the Princess, probably to differentiate between them and the Patriarch, who has a much darker complexion.
But yeah, in the end, nobody knows what really happened, as a consistent timeline is pretty much inexistent.
It would be really nice if Larian would clear up these questions by presenting an updated timeline or, at the very least, tell us which games are still canon and which are retconned (please don't retcon Divinity II: ED)
The only information regarding the continuity I could find was this tweet by Swen:
https://twitter.com/LarAtLarian/status/919812290098147328If I understand it correctly, this would mean that Div II: ED is still canon, but I'm not really sure.
